Drawing continuous sheet glass



JOSEPH P. CROWLEY, OF TOLEDO. OHIO, ASSIGNOR TO THE LIIBBEY-OWENS SHEET GLASS COMPANY, OF TOLEDO, OHIO, A CORPORATIQN OF OHIO.

RAWING CNTINUOUS SHEET GLAss.

Application filed Junes.

To all whom it may concern Be it known that I, Josnrr P. CROWLEY, a citizen of the United' States, residing at Toledo` in the county of Lucas and State of Ohio. have invented new and useful Improvements in Drawing Continuous Sheet Glass, of which the following is a specfication.

This invention relates to a'new process and apparatus for drawing sheet glass, and is more particularly, an improvenent in the process of drawing sheet glass horizontally from a source of molten glass.

In processes heretofore known, the sheet has been drawn horizontally from an overflow lip, or from the end of a horizontal or inclined slab, ontowhich the glass flows in a nolten stream, and the transition from the molten to the solid form 'takes place at the edge of the lip or slab, or after the plastic glass has been drawn therefrom. The diticulties encountered with all such systems, are largely due to the fact that the excess of molten glass overflows down the edge of the drawing lip, eventually devitrifying at this point, and forming accumulations of dog-metal, which cause lines and other defects in the sheet.

In this present improved system, the molten glass flows out from the source onto a slab of graphite or similar material which will not adhere to or injure the hot glass, and the glass is cooled and stretched or attenuated into sheet form while still remaining on the slab, so that before leaving the surface of the slab i't has assumed a practically solid sheet form, although still semiplastic, and capable of being stretched through a combined drawing and flattening 0 apparatus, such as now used in the wellknown Colburn process of drawing sheetglass.

The invention will be more clearly understood from the following detailed description of two examples of apparatus well adapted to carry out the principles of the invention. i

ln the accompanying drawings:

Fig. 1 is a longitudinal vertical section through one form of the apparatus.

Fig. 2 is a similar view of a modified construction.

Fg. 3 is a vertical transverse section, taken substantially on the line 3-3 of Fig, 2.

1921. Serial No. *175,291. v

Fig. 4 is a section through a modified form of slab.

Referring first to Fig; 1, the molten glass 1, flows out at 2, from the end of the refining chamber 3 of a continuous tank furnace, or other suitable source of supply, onto the slab 4. which is preferably mounted in the slightly inclined position indicated in Fig. 1. This slab is composed of graphite or some suitable compositionto which the molten glass will not adhere, and on which the solidifying semi-plastic sheetmay be drawn and stretched without being injured thereby. Such slabs can be constructed of so-called graphite-clay` a mixture of clay and graphite in proportions which are Varied according to the conditions under which the material is used. The clay gives strength and stability to the slab, while the graphite forms a smooth, non-scratching surface, to which the glass does not adhere. i

If desired, the slab may be constructed as shown in Fig. 4, of a lower section 5 of clay or other refractory material, and a surface layer 6 of graphite, or graphite-clay conthe slab. Beyond the lip-tile 11, a cooler M y (preferably of the type through which water flows continuously), is located in a cooling chamber 15. The temperature of this chamber may be regulated by raising or lowering the shea'r-cake 16, or by removing the plage 17 in the side-walls, whereby the cooling air from without is allowed to enter.

From the chamber 15, the glass sheet 18 is drawn' out between coolers 19 and 20, and through the arched cooling chamher 21, which. is open to the air at its sides 22. Cooler 19 is carried by yokes 23, adjustable vertioally by the screws 24, while cooler 20 is adjust ed vertically by the screws 25 adiacent its end's. While passing through chamber 21, the sheet is carried by the supporting rolls 26. The sheet then passes into the drawing and flattening mechanem MES ing freelythrough a slot 38 in the 27, which may be of any suitable type,

'but is shown of the form now used in the mechanism 27 must be operted at such' a speed that the glass will be drawn from the slab faster than it fiows thereon, and thus stretched or attenuated into sheet form as shown in the drawings. As the stream of molten glass assumes sheet form, and becomes partially set, it ceases to flow along the slab but slides the reon, so that before the outer end of the slab is reached, the glass is sliding on the graphite surface in sheet form. In this way there is no accumulation of molten glass .to form dog-metal at the end of the slab, and hence no lines or other defects will be drawn into the glass sheet. The sheet leaves the surface of the sla'b near the end thereof, passin of? between the coolers 19 and 20, whic help to set the sheet in its final form, this setting process being also accelerated b the cooling air passing through the open c amber 22.

In the form of apparatus shown in. Figs. 2 and 3, provision is made to vary the nclination of the drawing slab 28 to control the rate of flow. As in the form reviously described, the molten glass 1 ows out at 2 from refining tank 3, passin under lip-tile 11, onto the slab 28. As be ore the glass flows under the cooler 14, where it is reduoed to a viscous state, and is then drawn o as a sheet between coolers 19 and 20, and over 'supporting rolls 26' in cooling chamber 21, open at its sides 22.

In this form of apparatus 'the slab 28 is so formed at its inner end 29 that it can pivot at the outlet of the tank 3; and the outer end 29' of the sla-b is carried by a cooled cross-shaft 30, through which cooling fluid may be passed through pi e connections 31. At each end the sha 30 is carried by a link 32, mounted in a yolne 33, at the u per end of a screw 34, su port/ed in an a ;usting nut' 35. 'The sha t 30 is guided up and down in the arcuate slotted guides 36. By suitab ly adjusting the nuts 35, the outer end of the slab 28 ma be rased or lowered, thus varying the inc ina;- tion of the slab, and hence the rate of flow of the molten' glass, and the resistance to the drawing operation.

A block of refractory material 37 is suspended from the shaft 30, its lower end i" wall. This block forms the front wall of heating chamber 39 bene-ath the slab 28, this chamber being heated by suitable burners such as 40.

In this case, the temperature in the cooling and drawing chamber 41, above the slab is regulated by raising or lowering the block of refractory material 42, Suspended by cables 43 from any suitable adjusting means, not illustrated. This Will vary the effective Volume of the chamber abovethe drawpoint, and also eXpose the glass more or less to the action of coolers 14 and 19. The portion of chamber 41, above block 42 is open to the air as at 44.

It will now be understood, that this invention is a combined flowing and drawing system, the glass being supported throughout the transition period upon a slab of solid material which Will not adhere to, or in :m: way mar the surface of the glass.

hroughout the following claims, it is to be understood that whenever graphite is mentioned, the term is intended to include such mixtures of graphite and clay, or other similar substances, as would give the results previously described.

Claims:

1. The method of forming sheet glass, consisting in owing a stream of molten glass directly onto a heated slab, cooling the glass while on the slab, and drawing the gla across and from the sla'b faster than t flows thereon, so that it is attenuated and set in sheet form before it leaves the surface of the slab.

2. The method of forming sheet glass, consisting in flowing a stream of molten glass directly onto a gra hite slab, cooling the glass while on the s lab, and drawing the glass across and from the slab faster than it flows thereon, so that it is attenuated and set in sheet form before it leaves the surface of the slab.

3. The method of forming sheet glass, consisting in fiowing molten glass from a source of supply, and then drawing away the fiowing glass faster than it fiows from the source so that it is attenuated into sheet form the glass being su ported during the transition period upon t e flat face of a heated slab, and leaving the slab in sheet form before reaclu'ng the end of the slab,

drawing theglass along and from the slab in sheet form before the glass has reached the lower-end of the slab.

'6. In an apparatus for drawing sheet glass, an inclined graphite slab, means forflowing molten lass onto the slab, and means for stretc ing-.the glass into sheet form.- whileon the slab.' i

7. In an apparatis for drawing sheet lass, an inclined graphte slab, means ad- ;acent the hi her end of the slab for flowng molten ass thereon means for cooling the glass w ile on the siab; and means for drawing the lass along and from the slab in sheet form efore it has reached the lower end of the. slab.

8. In an apparatus for drawing sheet glass, an inclined graphite slab, means for flowing molten glas onto the slab, means for cooling the glass while on the slab, and means for st'etchi' gb the glass into sheet form while on the sl 9. An apparatus for drawing ,sheet glass, comprising a tenk containing molten glass,

,a drawing slab pivoted to the tankoutlet so that the molten glass may flow out onto the slah, means for adjustably supporting the free end of the slab, and means for stretehing the glass into sheet form while on the slab.

10. An apparatus for drawing sheet glass,

comprising a tank containing molten' glass, a graphite drawing slab pivoted to the tank outlet so that the molten glass may flow ont onto 'the slab, means for adjustab ly supporting the tree end of the slab, and

means for stretching the glassinto sheet 'formwhile on the slah. g

11. An apparatus for drawing sheet glass,

. eomprising a tenk containing molten glass,

a graphite drawing slab pivoted to the tanjk oatlet so that 'the molten glass may flow s'o that the molten glass flows out onto the slab, a eooled supporting shaft for the free end of the slab, means' for adjusting the shaft vertically to'vary the inclination of the slab, means .for cooling the glass while on the slab, and means for stretching the glass into sheet form while on the slab.

13. An apparatus for drawing sheet gla ss, comprising a tank containing molten glass, a graphite drawing slab pivoted to the tank outlet se that the molten glass flows out onto the slab, a eooled supporting shaft for the free end of the slab, means for adjustingthe shaft vertically to vary the inclination of the slab, means for cooling the glass while. on the' slab, and means for stretching theglass into sheet'form while onthe slab.

14. An apparatus for drawing sheet glass, comprising a tank containing molten glass, a graphite drawing ,slab pivoted to the tank outlet so that the molten glass flows out onto the slab, a. cooled supporti shaft for the free end of the slab, means or adsting the shaft vertically to vary the inc ination of the slab, a. heating chamber beneath the slab, the front wall' of the chamber being vertically adjustable with the slab, means for cooling the glass while on the slab, and means `for stretching the glass into sheet form while on the slab.

Signed at Toledo, in the countyof Lucas and State of Ohio, this 3d day of June,

JOSEPH CROWLEY. 

